1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a high temperature bearing in a gas turbine engine.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A small gas turbine engine of the type that operates near or above 100,000 RPM requires high speed bearings to support the single or twin rotors. In a twin spool gas turbine engine, the high speed shaft requires damping for the bearings because of the excessive vibrations due to rotor dynamics issues. Without adequate damping of the bearings, the rotor shaft could not operate at these high rotational speeds and thus an engine of this small size would not be practical.
Another issue with a small gas turbine engine is that the bearings are exposed to very high temperatures because they are located near the combustor or the turbine. Prior art dampers like those made of plastics cannot be used under these extreme temperature environments. Another type of damper is needed for use in high temperature environments like those in a small gas turbine engine, and that can provide the dampening capability for these high speed rotor shafts in order to make the small gas turbine engine workable.
Another issue is a long storage life before the engine is used. For a UAV of the kind used by the US Army as a surveillance aircraft, a long shelf life of as much as 20 years is required of the engine. The engine must be capable of still operating after sitting on a shelf for up to 20 years. Plastic O-rings have been used to provide damping for bearings. However, the plastic material would degrade over time due to oxidation and even from micro-organisms growing that harm the plastic. What is needed is a long shelf life bearing damper as well.